Packard Forum Index » V-8 (1955-56)

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https://packardinfo.com/xoops/html/modules/newbb/viewtopic.php?topic_id=1364&forum=3&post_id=11283#forumpost11283

Forged crank a later 56 service part:

That makes me wonder if the forged crank offering mite have been somekind of answer to the MIddle main bearing wear problem that has been discussed several times in the past.

Kanter actually lists .60 under bearings. The rods are ok.

I'm using a 320" crank I got from Eric in a performance build with light forged pistons and lightened rods. My assumption was the 320" pistons were lighter, thus the crank would need less balance weight removed.

Maybe it's time for me to put the 320" and the 352"/374" side by side and educate myself as to the differences of the two.

In fact, anyone got a 320" piston and a gram scale handy? That would be the quickest answer.

jack vines

Jack, I don't have one to weigh, but the specifications say they are different:

22.293 ounces for the 320 engine
24.763 ounces for the 352 engine
26.067 ounces for the 374 engine

Hi, Owen,

Thanks for the info. My only Shop Manual is a '56 and didn't have the 320" specifications.

Interesting in that the 320" piston is .1875" smaller diameter and 2.47 ounces lighter than the 352" piston and has its' own crankshaft.

The 352" piston is .125" smaller and 1.3 ounces lighter than the 374", but can use the same crankshaft.

jack vines

I doubt that any variation in the 320 crank has anything to do with piston weight. Most likely the 352/374 crank has narrower counter weights than the 320 crank to allow for the 352/374 piston clearence.

It will be most interesting to see what u find in crank differences between 320 and the 352/374 cranks. I onlu have cranks from 352's arounf here.

Quote:

The Service Counselor article referred to above mentions that "---the crankshafts used with 4" pistons are balanced differently than those using 3 13/16" pistons---" and goes on to say that the cranks for 4" bore are stamped with the number 4 and those for the 3 13/16" bore are stamped with the number 3.
There is a correction published in SC Vol. 29 No. 8 that says crankshafts stamped with the number 4 can be used for either bore size but those stamped with 3 can only be used for the smaller bore.

pic of 55-352 crank with number 4.

Hank

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In addition to the very good info from the aforementioned SCs, our online Service Index also references SSB No. 350, of December 1959, which advises that P/N 476009 - the crankshaft for 5560-80 (with 352 engines) all 1956 models - was replaced by P/N 440989 - a drop-forged shaft, with no holes/opening through the rod throws.

P/N 476009 is listed in our archived copy of the 55-56 parts book (updated through July 1, 1956) for both 5560-80 (with 4" bore) AND all 56th Series (with 4-1/8" bore), which would have been stamped with a "4".

Perhaps the crank that Randy has is P/N 440989, then. Any casting numbers or other identifying marks on that one?

Last but not least, the article advises that P/N 440912 was available for 5522-42-47 models (with 320 engines). However, it does not specifically state that this one supersedes P/N 440954, as shown in our copy of the parts book, which would have been stamped with a "3", or whether it was forged.

So, now we have FOUR different crankshaft parts numbers to consider for the V8s.